A judge at Spain's top criminal court opened an investigation into former Spanish football federation president Luis Rubiales on Monday, following a lawsuit filed over his forcible kiss on Jenni Hermoso's lips after the Women's World Cup final.

Judge Francisco de Jorge of the National Court, admitted the complaint filed by Spanish prosecutors last week regarding alleged "crimes of sexual assault and "coercion", the court said in a statement.

The magistrate also asked media outlets to send him footage from different angles of Rubiales' kiss, as well as the Spain players' celebrations in the dressing room and on the team bus after winning the World Cup on August 20 in Sydney.

The public prosecutor's office filed a complaint against Rubiales last week, requesting that "a statement be taken from Luis Rubiales, as a defendant, and from Spain midfielder Jenni Hermoso as a victim".

Since a recent reform of the Spanish penal code, a non-consensual kiss can be considered sexual assault, a criminal category that groups together all types of sexual violence.

The penalties for a forced kiss can range from a fine to four years in prison, according to sources from the public prosecutor's Office.

De Jorge's decision came the day after Rubiales announced his resignation as Spain's RFEF football federation president, after initially refusing to do so claiming that the kiss had been "consensual".

In an open letter announcing his decision the 46-year-old continued to defend himself.

"I have faith in the truth and I will do everything in my power so that it prevails," Rubiales wrote.

Australian police told AFP on Monday they were willing to help with an investigation, but that a report had not yet been referred to them.

Hermoso, 33, who plays for Mexican club Pachuca, has said the unwanted kiss left her feeling "vulnerable and like the victim of an assault", with a statement on social media describing it as "an impulsive, macho act, out of place and with no type of consent on my part".

She also accused Rubiales of pressuring her to speak out in his defence immediately after the furore over the kiss erupted, which prosecutors said could be considered a crime of coercion.